Logical Fallacies

Introduction

If you want to be a skilled rhetorician, you’ll want to understand logical fallacies, or mistakes in reasoning. Not only can you then avoid them yourself, but you can take great delight in pointing out where others have erred.

On this page we review the most common logical fallacies.

Common Fallacies

Ad Hominem

An Ad Hominem argument (from Latin for to the man) is a direct attack on the character and ethos of a person. Instead of dealing with the issue or idea, the speaker questions the credibility of the source:

Al Gore has made a career out of scaring people with his theory of climate change. Yet Gore is a hypocrite. Not only did he sell his cable network, Current TV, to Al Jazeera, which is funded by oil-producing Qatar, but he also leads a lavish lifestyle traveling around the world and consuming much more electricity than the average American.

While it’s a valid strategy to attack the credibility of a court room witness, in public discourse ideas should often be considered separately from the people who promote them.

Strawman Fallacy

Think of a strawman as a scarecrow in the fields. It’s easy to push over because it can’t fight back. In the same way, a strawman argument occurs when you sum up an opposing view in such a way that it is easy to defeat. Simply put, you’ve made a caricature of someone else’s ideas. Here’s an example:

Opponents of capital punishment claim that all killing is wrong. They make no distinction between the killing of a serial killer and the death of our country’s enemies in war. They oppose all legitimate police violence in defense of law and order. They even oppose our right as citizens to defend our property by being willing to shoot to kill.

In this passage, the writer has characterized critics of capital punishment as opposing all killing, which is an unfair charge.

Stereotyping

Stereotyping or generalizing is common enough. Here is a sports commentator speaking about European ice hockey players:

This NHL season there has been an increase in high-sticking penalties. Most of the players that do it were trained in Europe. They wear visors themselves, and so perhaps they don’t understand the danger. But that’s not how we play in North America.

Non Sequitur

The Latin phrase non sequitur means it does not follow. A non sequitur is a break down in logic, where A is falsely said to have caused B. Here are some examples:

Since you’re a fan of rock music, you will love Pink Floyd’s The Wall.

Because you’re a good speaker, you’ll make an excellent salesman.

John is very concerned about what he eats; therefore, he will be an excellent dietitian.

Either Or Fallacy

An either or fallacy is the mistake of thinking that there are only two options in a given situation:

Those countries have been at war for far too long. Either we send in the troops now or this violence will go on forever.

If we assume that something has to be either this or that, we ignore other viewpoints in favour of polarizing opinions.

Post Hoc Ergo Propter Hoc

The Latin phrase post hoc ergo propter hoc means after this, therefore because of it. A post hoc argument assumes that because B happened after A, B must have been caused by A. Here is an example:

After he was elected, there were fewer incidents of racially motivated violence. His leadership made a difference in overcoming racial conflict.

Just because one thing happened after another doesn’t mean there is a causal connection.

Bandwagon Appeal

To jump on the bandwagon means to support whatever is popular or fashionable.

A bandwagon appeal is the mistake of thinking that if enough people have an opinion about something, they must be right:

Israel was certainly wrong to invade the Gaza strip.  Not only most Middle-Eastern nations, but also many western countries were against it.

Most respectable people don’t smoke.

Remember that the majority is not always right.

Slippery Slope Argument

A slippery slope argument assumes that if A happens, B, C, and D are sure to follow:

If you keep hanging around with those friends, pretty soon you’ll be a druggie.

For now they say they’re only interested in banning the carrying of concealed weapons. Before long, though, they’ll even try to take away your right to own private property. It’s time to take a stand against these communists.

Conclusion

As you evaluate the strength of an argument and check for logical fallacies, here are some things to consider:

• Can you think of exceptions to any of the premises or parts of the argument?
• Are all aspects of the question considered? What kind of proof or evidence is used?
• To what extent are the arguments based on pathos, logos, or ethos?
• Has the writer summed up the opposing view adequately and fairly?